Ignition system for combustion engines



Feb. 26, 1957 w. B. SMITS xcumou SYSTEM FOR COMBUSTION ENGINES 2 Sheets-Sheet 1 Filed April 10, 1952 Feb. 26, 1957 w. B. sMn's IGNITION SYSTEM FOR COMBUSTION ENGINES Filed April 10, 1952 2 Sheets-Sheet 2 INVENTOR 140725 55x5 5/v/7s,

BY i Kw B Q ATTORNEY United States Patent 2,783,289 IGNITION SYSTEM FOR COMBUSTION ENGINES Wytze Beye Smits, Voorburg, Netherlands, assignor to Smitsvonk N. V., Rijswijk, Netherlands, a company Application April 10, 1952, Serial No. 281,543

3 Claims. (Cl. 12314S) The invention relates to an ignition system for internal combustion engines.

In the electric ignition devices known in the art, with battery ignition, use is generally made of a primary circuit, a. secondary circuit, a mechanically driven current interrupter in said primary circuit to open and close said circuit and a distributor mechanism, a current impulse being produced in the primary circuit, connected to the battery, by the opening and closing of the said primary circuit. Through the interruption of the primary circuit a current impulse of a much higher voltage is induced in the secondary circuit, and this impulse causes the ignition spark proper to jump. In order to pass on this current impulse to the individual ignition spark plugs mounted in the cylinders of the internal combustion engine, when there are several cylinders a so-called distributor mechanism has been built in, which passes onthe current impulses produced in the secondary circuit in the correct order to the individual ignition spark plugs. However, the moment of the spark, the so-called timing, is determined by the interrupter device, the means by which the ignition spark is induced. From this it is evident that the opening of the primary circuit should take place at the same moment at which the distributor passes on the ignition current impulses thus induced to the ignition spark plug. of the cylinder in which the gas mixture is to be ignited. It is further evident that the connection between the interrupter and distributor must thus be a rigid one, so as to guarantee a comparatively correct timing of the ignition in this case.

It has been found that to obtainoptimum results with an internal combustion engine the moment of ignition in relation to the'position'of the; piston should vary with different engine loads.v For. example, the, moment of ignition may vary between the top dead centreposition of the piston to, in some cases, 20 before the top dead centre position. Constructions had to be used which guaranteed this variability in the drive of the interrupter mechanism and the distributor mechanism rigidly connected thereto. Various constructions were used for this purpose, for example vacuum regulators, centrifugal regulators or mechanical hand-operated regulating devices.

In present known ignition systems for internal combustion engines, the distributor shaft is directly connected through a gear train to the engine cam shaft. An intcrrupter cam is mounted on the distributor shaft to operate the interrupter points in the primary circuit and thus to control the current impulses in said circuit. Mounted on the distributor shaft is also the rotor which distributes the current impulse created in the secondary circuit to the various contact points of the distributor leading to the various spark plugs of the engine. As indicated above, the primary current impulses provide for the production of the requisite spark in the secondary circuit, and determine the moment at which sparking takes place in said circuit, or the so-called timing.

The responsiveness or timing of the spark in the secondary circuit depends Qnthe condition of the contact points 2,783,289 Patented Feb. 26, 1957 as they do in due course of time, the timing becomes inaccurate, even though a good spark may still be produced. If the pressure of the contact hammer in the interrupter becomes too weak, neither the spark nor the timing will be good. When the hammer becomes too stiff, a good spark may be produced, but the timing cannot be good. If the distributor and interrupter are accurately timed so the interrupter functions prematurely, the points of the distributor are eroded as the spark from the ignition coil jumps the gap between the distributor points. If the interrupter and the distributor are inaccurately timed so that the distributor closes prematurely, a weak charge is provided at the plug. v

The present invention overcomes the difiiculties outlined above through the use of low tension spark plugs which have been developed. By the use of low tension spark plugs the plugs may be fired by condenser discharge which permits the arrangement ofparts in the ignition circuit in a novel manner. By using 3,000 volts instead of the usual 10,000 to 12,000 vol-ts, the charge of the condenser will not jump the distributor spark gaps so that the interrupter and distributor .need'not be in time relation. The discharging condenser need only be charged in the periods between the passage of the distributor rotor from one contact point to the next. 7 The only thing necessary is the constant production of a good contact for producing a current impulse in the primary winding, so that a suflicient amount of energy for charging the discharging condenser is produced in the secondary circuit.

-In high tension ignition systems, a second drawback resides in the use of centrifugal weights with the cam of the interrupter. As indicated above, the spark must be regulated to insure maximum performance or the engine at different speeds and loads. The centrifugal advance is obtained by attaching to the interrupter cam a weight, so that as the speed of the engine increases, the movement of the weights under centrifugal force advance the angular position of the cam relative to the drive shaft- In this new position the points open at an earlier time than before andv therefore the spark is advanced. To insure a good spark in the primary circuit, suflicient pressure must be applied to the interrupter hammer to bring the contacts together. This pressure must be overcome by the action of the centrifugal weights, thus requiring relatively heavy weights, and a complicated mechanism. It has thus been necessary to develop highly complicated centrifugal regulators, adjusted to the characters of a given type of engine, dependent on the voltage required and the fuel consumption. The heavy contact pressure in the primary 1 circuit often caused serious dilficulty;

, used in the economy operating ranges of the engine. This has usually been a diaphragm acted upon by manifold pressure against spring resistance rotating the entire interrupter-point plate. The same drawbacks discussed above are encountered in this device.

In low tension systems with surface discharge spark plugs, howeventhese drawbacks are eliminated, when according to the invention, the interrupter is no longer driven by the driving shaft for the distributor arm, the

so-called loose shaft, but by a member rigidly connected to the engine shaft, for example the so-called fixed 1 driving shaft for the centrifugal or vacuum regulator. To this end the said shaft may be provided with a rigidly connected cam controlling the distributor and having nothing to do with the regulator. This has the advantage that the primary contact can be designed so as to exert as much pressure as is desirable or necessary, since this contact only has to induce a current impulse, while it is no longer concerned in the timing of the induction.

An. additional advantage of this different drive of the distributor, according to the invention, is that the centrifugal or vacuum regulator may be very compact, because now it only has to drive the distributor arm, which does not meet with any resistance. Because the interrupter according to the invention can be located in any desired place and be driven by a member coupled to the engine shaft, the latter may, for example, be provided near the ignition coil, so that the other long cable connections required are eliminated. The invention is explained more in detail with reference to the drawing illustrating a number of embodiments.

Fig. 1 is a diagrammatic illustration of the ignition system hitherto used for high tension spark plugs.

Fig. 2 is a diagrammatic illustration of the low tension ignition system according to the invention.

Fig. 3 is a diagrammatic illustration of the low tension ignition system embodying a distributor casing supporting the stationary contact and a vacuum advance means adapted to rotate said casing.

Fig. 4 is a diagrammatic illustration of the low tension ignition system embodying in a combination the concepts of Fig. 2 and Fig. 3.

Fig. 5 is a diagrammatic illustration of the low tension ignition system disclosing a vacuum operated braking means controlling the centrifugal displacement of the weights as an alternative to the embodiment disclosed in Fig. 3.

Fig. 6 is a diagrammatic view of a complete ignition system disclosing the concepts of the invention in relation to said ignition system.

According to the system of Fig. 1, the driving shaft 1 becomes the fixed shaft driven by the engine, and this is provided in the usual way with a bushing 3 containing the centrifugal regulator 4, which drives the disc 5 by means of the pins 6 engaging therein, the disc drives, via a cam (not hown),,the loose driving shaft 2 of the distributor arm 7. Owing to the greater or smaller amount of displacement of the weights of the regulator 4, the disc 5 is turned in relation to the shaft 2, and the engine will operate with more or less pre-ignition. On the shaft 2 is also mounted the distributor cam 9, which provides for the interruption at the'right moment of the primary contact of the ignition system. This distributor cam 9 thus provides for the production of the spark and for its timing.

According to the invention, on the other hand, as disclosed in Fig. 2, the distributor cam is no longer driven by the loose shaft 2, but by another member, rigidly connected to the engine, for example a cam rigidly secured on the shaft for producing the spark (Fig. 2). In this system therefore the distributor earn 9 provides for the production of the spark, while the distributor arm 7 provides for the timing, and the ignition condenser can now be charged in the periods between the passage of the distributor arm from one distributor contact 8 to the next.

Fig. 3 illustrates a construction provided with a distributor casing 10, inwhich the stationary contacts 8 are accommodated. By means of the diaphragm 11 operated by vacuum action--caused by the suction pipe or" the engine-the entire distributor head system can be displaced slightly in relation to the direction of rotation of the distributor arm 7, so that the effect of earlier or later ignition is obtained.

Fig. 4 shows a combination of the systems according to Figs. 2 and 3, in which the shaft 2 is displaced already in relation to the driving shaft 1 by means of mechanical weights, while in addition to this the distributor head 10, with the stationary contacts 8 accommodated therein, can be displaced by means of the vacuum device 11, so that the degree of displacement in relation to the distributor arm 7 can be decreased or increased. Finally, Fig. 5 shows a construction in which, by means of a braking mechanism 12, the disc 5, which is displaced by the flying weights and is coupled to the shaft 2, is braked in its displacement in relation to the shaft 1 by the said braking mechanism 12, which in turn is operated by a vacuum device connected to the suction pipe of the engine.

Fig. 6 relates to the above embodiments with respect to the ignition system as a whole. Fig. 6 discloses the distributor cam 9, opening and closing the interrupter points in the primary circuit connected to the battery. The secondary circuit comprises the condenser distributor arm or rotor 7 and the distributor points leading to the various spark plugs, designated by the crosses. In the present invention, it is thus the advancement or retardation of the distributor points 8 as disclosed in Fig. 3, or the distributor arm 7 as disclosed in Figs. 2 and 5, that is controlled.

Having disclosed the invention, what is claimed as new and novel is:

1. In an ignition system for low voltage surface discharge spark plugs which are adapted to be operated on condenser discharge, comprising a distributor cam driven directly by an engine shaft, a circuit interrupter operated by said cam, said circuit interrupter operable to charge an ignition condenser, a distributor, means for shifting the position of said distributor to vary the time of dis charge of the condenser through the spark plugs, said last-named means operating independently of the timing of the distributor cam and circuit interrupter.

2. An, ignition system according to claim 1 in which said last-named means is a centrifugal regulator.

3. An ignition system according to claim 1 in which said last-named means is a vacuum regulator.

References Cited in the file of this patent UNITED STATES PATENTS 1,034,778 Foster Aug. 6, 1912 1,459,252 Plumm June 19, 1923 1,466,209 Eichbaum Aug. 28, 1923 2,472,671. McNulty June 7, 1949 2,489,780 Hooven Nov. 29, 1949 

